Consistently, it has been reported that Per2‐deficient mice maintain vigorous DDR and the lengthy cancer‐free lifespan.36 Previous studies showed that the oscillation of DDR could be ascribed to the circadian rhythm of XPA (DNA damage recognition and repair factor) expression in antiphase with CRY1 or in normal phase with BMAL1.[qv: 18b,37] Conversely, in OSCC cells, we observed that the rhythm of DNA adducts repair markers (DDB2, ERCC1, XRCC1, and POL‐β) is in antiphase with PER2. The gene discussed is XRCC1; the disease is cancer.